Are Class-D Amps Ready For Prime Time? - Page 6 - AVS Forum | Home Theater Discussions And Reviews
View Poll Results: Are Class-D Amps Ready For Prime Time?
Yes 285 73.26%
No 34 8.74%
Don't know 70 17.99%
Voters: 389. You may not vote on this poll

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post #151 of 210 Old 02-17-2016, 04:30 PM
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Quote:
Originally Posted by Kev H View Post
Class D Audio is a brand. Here's a link to its website: http://www.classdaudio.com/ .

I'd like to know how many of us have heard of them, who's interested in them, who might take the plunge as I have, and who has decided not to and why.

That's what I'm asking.
Nice find. I am 99% sold on these. I plan to pair one of their 2-channel amp offerings with an Emotiva Stealth DC-1 DAC/preamp.

However, I don’t see a 12V trigger. Will these power on/off with line voltage, or you have to manually power it on & off via the side-mounted rocker switch?
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post #152 of 210 Old 02-17-2016, 04:32 PM
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Quote:
Originally Posted by Radio81 View Post
Nice find. I am 99% sold on these. I plan to pair one of their 2-channel amp offerings with an Emotiva Stealth DC-1 DAC/preamp.

However, I don’t see a 12V trigger. Will these power on/off with line voltage, or you have to manually power it on & off via the side-mounted rocker switch?
It's a manual thing.
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post #153 of 210 Old 02-17-2016, 05:47 PM
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Originally Posted by highfigh View Post
And how would you take a low voltage/current signal from source devices, send it to a transducer and achieve adequate SPL without dealing with voltage, current and load?
No transducer.

No low-level signal.

No load.


Look, this technology is old, old, old. The reason we have amplifiers is to drive a piston with a linear motor. (in most cases).

The whole idea is silly. Completely. It is a nearly open-loop system from the terminal of the linear amplifier to the piston-motor. That's just bonkers from a control-theory standpoint.

Start with a clean sheet, absolutely clean, and ask the question: "How to reproduce the sensation of sound?"

So, what kind of machine is required to do that? We've been using the magnetic loudspeaker, in nearly unaltered form for 100 years now.

Perhaps - it can be done better, no?

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post #154 of 210 Old 02-17-2016, 08:25 PM
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Quote:
Originally Posted by nuke View Post
No transducer.

No low-level signal.

No load.


Look, this technology is old, old, old. The reason we have amplifiers is to drive a piston with a linear motor. (in most cases).

The whole idea is silly. Completely. It is a nearly open-loop system from the terminal of the linear amplifier to the piston-motor. That's just bonkers from a control-theory standpoint.

Start with a clean sheet, absolutely clean, and ask the question: "How to reproduce the sensation of sound?"

So, what kind of machine is required to do that? We've been using the magnetic loudspeaker, in nearly unaltered form for 100 years now.

Perhaps - it can be done better, no?
No transducer? How would you get the data to the listener's ears?

If you want to connect people to the source electrically, good luck with that. We know it can be done, but with what kind of fidelity?

"Unaltered"? Hardly, unless you mean that an electric device makes sound and then, I agree but how would you make sound go from one place to another?
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post #155 of 210 Old 02-18-2016, 05:57 AM
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Quote:
Originally Posted by Kev H View Post
Class D Audio is a brand. Here's a link to its website: http://www.classdaudio.com/ .

I'd like to know how many of us have heard of them, who's interested in them, who might take the plunge as I have, and who has decided not to and why.

That's what I'm asking.
This is a class d topology thread... not a class d brand thread.

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post #156 of 210 Old 02-18-2016, 09:31 AM
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Class D amplifiers are not 'digital'.

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post #157 of 210 Old 02-18-2016, 09:40 AM
 
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Originally Posted by W4RLORD View Post
Class D amplifiers are not 'digital'.
So what class of amplifiers are?
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post #158 of 210 Old 02-18-2016, 01:12 PM
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Smile New Thread in Receivers, Amps, and Processors Forum

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Originally Posted by MSchu18 View Post
This is a class d topology thread... not a class d brand thread.
Thanks for the wonderful idea! I started a new thread!
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post #159 of 210 Old 02-18-2016, 05:20 PM
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Quote:
Originally Posted by MSchu18 View Post
Quote:
Originally Posted by Kev H View Post
Class D Audio is a brand. Here's a link to its website: http://www.classdaudio.com/ .

I'd like to know how many of us have heard of them, who's interested in them, who might take the plunge as I have, and who has decided not to and why.

That's what I'm asking.
This is a class d topology thread... not a class d brand thread.
Wow. Class D brand = Class D amps. Plz go
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post #160 of 210 Old 02-18-2016, 07:18 PM
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Originally Posted by johnplayerson View Post
It has and always will be the POWER SUPPLY, and not the method of amplification, that will determine overall performance.
I agree that a good PS, no matter the type, is important, but emphatically disagree with your implication that the output stage is not just as important.

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post #161 of 210 Old 02-18-2016, 07:20 PM
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It's rather tiresome to keep complaining about the state of things without offering any suggestions on how to improve.


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Originally Posted by nuke View Post
No transducer.

No low-level signal.

No load.


Look, this technology is old, old, old. The reason we have amplifiers is to drive a piston with a linear motor. (in most cases).

The whole idea is silly. Completely. It is a nearly open-loop system from the terminal of the linear amplifier to the piston-motor. That's just bonkers from a control-theory standpoint.

Start with a clean sheet, absolutely clean, and ask the question: "How to reproduce the sensation of sound?"

So, what kind of machine is required to do that? We've been using the magnetic loudspeaker, in nearly unaltered form for 100 years now.

Perhaps - it can be done better, no?

Noah
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post #162 of 210 Old 02-18-2016, 08:30 PM
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Originally Posted by noah katz View Post
I agree that a good PS, no matter the type, is important, but emphatically disagree with your implication that the output stage is not just as important.
I never said the output stage was not as important, nor was it implied. Most modern amplifcation stages are quite good for 20 to 20000k performance. With SMPS it has always been the need to improve the power supply to in effect improve the output stage.

You can have two identical, Class H three tier output stages, with one powered by the old school toroidal supply and the other powered by SMPS. The toridal supply will outperform the SMPS in both reliability and longevity, as well as in performance, mostly due to the fact a 22ms burst is not adequate for all audio applications. Just like you cant expect a car to go full speed on flat tires you cannot expect identical output stages to magically be equal with differentiated power supplies.

I am quite sure if you one gave Class D a toroidal supply, and another identical class D, an SMPS, the class D with the toroidal supply would outperform. IF you check most specifications on Class D units however, for some reason distortion is higher, but again we do not have a class D with a toroidal supply to compare to, to see if the supply would in fact make a difference in both distortion, and in output, that I claim it will, based on simple common sense.

They are beginning to make some SMPS power supplies with a lot more burst power than just 22ms. Meyer sound uses 100ms as standard for their power supplies. Speaker power claims to have an SMPS design that will not flat line at 500 watts rms when given a more continues signal. For the most part we still wait for the perfected SMPS supply that will equal Toroidal supplies for every audio application. Cost factors have dictated that consumer demand no longer dictates product development for amplifiers, rather manufacturer demand does, along with the pro audio industry which saves millions by having amplifiers of feather weight status. This creates the extra demand by manufactures to push SMPS and class D into the consumer realm, where many popular AVR's now employ complete 6 to 11 channel Class D output stages.

Unfortunately Old school is being driven out, because size and weights simply make the lighter versions more profitable and less costly for Pro audio use, and economies of scale in manufacturing have made SMPS very cheap to produce, while the reverse economies of scale due to less production, have made old school more expensive to produce. More and more old school gets discontinued every year, with only one main company that I know of claiming some of the abandoned space........ Emotiva.

As an audiophile myself I avoid SMPS, where ever I can for the long term reliability issue alone, never mind the performance issue. I believe the manufacturers do not build them to last on purpose these days. They can make them so much better with a few dimes and nickels, Instead they increase the prices even further, because the huge cash flow logistical savings for pro audio applications, increases the value of the product, while the construction cost of the product goes down. Heavy prices of SMPS devices is therefore not caused by production costs, but by
the cost flow savings created for pro audio.

They did not decrease there costs by 80 percent, just to hand over the money in savings to us. For home users I recommend people still to old school where ever they can, while they still can.

https://discuss.avscience.com/index.php?topic=459.60
A Good amplifier requires a adequate power supply, It does not matter what the amplifier is capable of if the power supply will not provide the power required. Most amplifiers have under rated power supplies. It is up to you to make sure you get the ones that are least under rated if at all.
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post #163 of 210 Old 02-18-2016, 11:56 PM
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Quote:
Originally Posted by Kev H View Post
Quote:
Originally Posted by MSchu18 View Post
Class D Audio is a brand. Here's a link to its website: http://www.classdaudio.com/ .

I'd like to know how many of us have heard of them, who's interested in them, who might take the plunge as I have, and who has decided not to and why.

That's what I'm asking.

You've taken the plunge with Class D Audio brand amplifiers. Any complaints?
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post #164 of 210 Old 02-19-2016, 12:26 AM
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No 12 Volt Trigger Is Not a Problem for Me

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You've taken the plunge with Class D Audio brand amplifiers. Any complaints?
No complaints yet. I'm only driving the Marimbas at the time being. As it looks now, I'm due to settle on a house in March. It has a listening space that is about 15'X18'X8'. So, new speakers will be purchased by year's end.

Who knows maybe a luck into something used that's hard to drive like a pair of Thiel CS 3.6 . Who knows? I bought this amp to be able to take any impedance and/or power issue off the table. I'd like audition the Martin Logan Motion speakers. Maybe Cambridge audio floorstanders as well. I like a speaker to have a big, open, airy sound without giving up any pace or rhythm quality. Do the Vandersteen 2ce do that? I don't know. I'd go with Magnepan but, I have cats.

Also, the unit does not have a 12 volt trigger. But this is not an issue for me. As a matter of fact, I haven't required that feature yet!

Also, if one needs to use speaker level inputs for a subwoofer, there is no need to install a capacitor in the hook-up, as is required by some older Bel Canto units.

Power on and off is strictly by the side rocker switch. The pop suppression circuitry is 100% effective, there is no pop!

I believe these units will last a lifetime!

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post #165 of 210 Old 02-19-2016, 02:50 PM
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Quote:
Originally Posted by noah katz View Post
It's rather tiresome to keep complaining about the state of things without offering any suggestions on how to improve.
Hmm. Something amazingly ironic that Noah has missed here entirely....


I have indeed, in this very thread, done precisely that.

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post #166 of 210 Old 02-20-2016, 01:30 AM
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I have an AVR with Class D amps from 2003 - still going strong - the Sony STR-DA2000ES. Still sounds great.

"Don't forget that a significant contribution made by the use of high-end cabling is emotional. Knowing that you have the best available causes the listening and viewing to be that much more enjoyable. Observable improvements make it even better."

-From a post on the audio video improvements forum
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post #167 of 210 Old 02-22-2016, 06:09 AM
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I have an AVR with Class D amps from 2003 - still going strong - the Sony STR-DA2000ES. Still sounds great.
"Sounds great" is relative. Swap in a well regarded class A/B and you will hear a significant improvement. Today's Class D is finally taken seriously. Not so much many years ago.

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post #168 of 210 Old 02-22-2016, 11:43 AM
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"Sounds great" is relative. Swap in a well regarded class A/B and you will hear a significant improvement. Today's Class D is finally taken seriously. Not so much many years ago.
Dude I also have a $2,000 2009 Sherwood R-972 with Trinnov and a $3,000 2016 Denon AVR-X7200WA. Whether or not you or anyone else in 2003 "took Class D seriously" (whatever that means) I do not think you could distinguish the sound in a blind test.

If you think you can hear a difference I invite you come on by my home next time you're in So Cal and I'll give you a few hours with my system - and some Macallan 18 y/o single malt to sip on while you attempt to figure out which receiver you're listening to behind the curtain.

You can believe otherwise but until you hear these receivers playing music back to back reserve your judgement.

Now it is true that the Sony from 2003 did not have any room correction, subwoofer integration (Audyssey XT32) or speaker remapping (Trinnov) - for home theater use these autocalibration features do make my system sound better.

But for pure stereo music listening in a double blind test with no auto calibration routines running I do not believe you could tell the difference. The Sony's sound is incredibly clean. And as for power it has 120 watts per channel - rated with all 7 channels driven full range simultaneously.

Sony was ahead of its time - my opinion is that the 2003 era Sony Class D receivers were too clean, too precise, too accurate - and lacked all the distortions that pseudo-science-embracing audiophiles enjoyed calling "warmth" and other nonsense not reproducible in blind tests.
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"Don't forget that a significant contribution made by the use of high-end cabling is emotional. Knowing that you have the best available causes the listening and viewing to be that much more enjoyable. Observable improvements make it even better."

-From a post on the audio video improvements forum

Last edited by chrisreeves; 02-22-2016 at 11:49 AM.
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post #169 of 210 Old 02-22-2016, 12:30 PM
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Quote:
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I have indeed, in this very thread, done precisely that.
You mean this?:

Quote:
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Why limit this to devices which can only be driven by an analog, linear, audio signal?

Why not combine the mechanism and the electronics together as a tightly coupled system? Perhaps enabling technology that requires a completely non-linear electronic system to drive it? Or maybe a servo drive with direct feedback from the electro-mechanical system to arrive at linearity?

Perhaps something driven by multiple linear motors with each driven by a highly efficient servo H-bridge in the digital realm. The electronic drive designed to move the mechanical system of the transducer, without ever creating a recognizable audio waveform. Rather, it would generate the required signals to cause the transducer to produce the desired sound.

The whole idea of loudspeaker driven directly with an amplified, linear audio signal is very limiting and inefficient.
Why is a tightly coupled system better?

What are the benefits of a completely nonlinear system?

Multiple linear motors are far more complex and costly than voice coils, and have way more mass as well as stiction.


If you want to complain about archaic technology, how about jet engines, which produce forward propulsion by throwing a crapload of greenhouse gases out of the back.

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post #170 of 210 Old 02-22-2016, 04:15 PM
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If you want to complain about archaic technology, how about jet engines, which produce forward propulsion by throwing a crapload of greenhouse gases out of the back.
Well, even though you're moving to a non-sequitor here, I'll indulge you.

Modern jet engines don't work that way. You're describing the pure turbojet.

Modern jet engines, at least those used in sub-sonic aircraft, provide the vast majority of thrust from the ducted fan principle, thus are called turbofans. The turbine is used to supply mechanical energy to rotate the large fan and most of the thrust results from the fan, not the turbine exhaust. Modern turbofans have bypass ratios of 9:1 or better, some in commercial use up to 12:1.

--- Now getting back to topic-----

The premise of the conventional loudspeaker and amplifier is that the amplifier will build a very strong and perfectly accurate analog signal to feed to the voice coil(s) of the speaker, in the hopes that it will somehow turn this into a highly accurate audible representation of the original signal long ago, that impressed upon the microphone. Let's presume that the recording is what is intended to be heard, since we can't usually change the recording once it is made.

But let's look at the premise of the speaker/amplifier. It is a bit ludicrous to think that a mechanical system with all those resonances and unpredictable physical reactions can do this without any significant feedback or control loop.

Speakers are the big unknown in any playback system. They are the biggest source of distortion and coloration. Not only do they interact with their own components, the interact with the room and the objects in the room to a great extent.

If the ultimate goal of the machine is to vibrate the air as accurately as possible, wouldn't it make sense to use some sort of control loop in that process?

For instance, if you start with the standard coil/cone loudspeaker and measure its position and velocity and compare that to the intended function of the sound signal, you will find significant error. This goes far beyond simple corrections, like frequency response. Further, if you measure how that couples into the surrounding air, you'll find a great deal more error.

Now lets say you had a very powerful digital signal processor in the loop and it was programmed with all of the various transfer functions that accurately predicted what the speaker would mechanically do for any input condition and it could use the sensors integrated into the speaker to assure that it was doing just that, then the processor could take the original audio signal from the playback source, apply the necessary mathematical transformations and control calculations and cause the speaker to accurately excite the air with the signal.

You would have to expect that the current/voltage signal applied to the voice coil terminals, would look very, very different than what would come from a conventional amplifier. Yet, the net effect of the system would produce much more accurate vibrations into the air, which is the whole goal to begin with.

Such a system would allow for far more optimal design of the amplifier, speaker motors and enclosures than is possible from the conventional paradigm of "pretend it is perfect" and drive it hard.
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post #171 of 210 Old 02-23-2016, 12:43 AM
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... most of the thrust results from the fan, not the turbine exhaust.
Doesn't matter which part of the engine produces, bottom line is that all thrust is from Newton's 3rd Law; the force it takes to throw the crap out of the back pushes the plane equally hard forward.

Quote:
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It is a bit ludicrous to think that a mechanical system with all those resonances and unpredictable physical reactions can do this without any significant feedback or control loop...

...if you start with the standard coil/cone loudspeaker and measure its position and velocity and compare that to the intended function of the sound signal, you will find significant error.
That doesn't jibe with reality; good albeit expensive speakers have distortion well less than 1% without any of the complexity you suggest.

What you've offered is either vague, or more clumsy in implementation than current design.

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post #172 of 210 Old 02-24-2016, 07:01 AM
 
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I have the SC-05, which contains an older model of the Class D used in the SC-55, but it sounds great. I don't use it to drive full range speakers, only down to 80 Hz, so this may not really be taxing on the system, but I believe this is a real world case for most sit ups. On AVSForum, I heard that the x7 Amp (57, 37, 27, 07) does better on the low end.
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I am not sure what is meant by primetime so I'll infer it to mean reference audio applications, but I understand that the OP may have meant something else.

I'm my experience, all of the amplifiers that I have listened to and or measured or both, that are based on switching power supplies have been inherently colored, and i have found that their colorations change not just with frequency but amplitude as well. Then there's the required need for heavy passive filter development, for implementation at the outputs, to roll off the top of the audio bandwidth to reduce the switching noise, etc.

To me they have a lot of applications were they can and are being used, but from a purist perspective, they are a far cry from being true reference class. Could their be an acceptation, sure can. But i personally have not been introduced to the acceptation.

All switching based amplifiers currently have elevated noise floors, its just the current state in the evolution of this class of amplification. They also have a lot more harmonic content throughout the entire bandwidth.

Beyond this, more and more of these types of amplifiers are coming equipped with internal compressors and limiters, which are not set optimally for all applications. I am not referring to the user adjustable filters but the ones at the firmware level. Variants with these preset are never optimal for reference applications, but highly applicable in many commercial PA applications.

A recent variation in the switching amp platform has been the i-class. which still suffers these common cons.

So as of today, my vote is - NO, d-class amplification isn't ready for primetime reference audio applications, but I'd say - Yes it is for most other applications.

One Caveat - I have not listened to or measured the new HD-D Class products which are boosting of the elimination of the many of the distortion problems, by using a high amount of negative feed-back. So after I get sometime with one of these amp's my opinion may change. Perhaps this variant will present an exception.
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post #174 of 210 Old 03-02-2016, 02:44 PM
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So as of today, my vote is - NO, d-class amplification isn't ready for primetime reference audio applications, but I'd say - Yes it is for most other applications.
Theta and NAD offer audiophile Class D.

All amps do not "sound great" just because they make speakers produce sound. I'd encourage the skeptics to check out the very, very few now doing Class D justice despite the message from the "all amps are great" crew.

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post #175 of 210 Old 03-02-2016, 03:20 PM
 
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Theta and NAD offer audiophile Class D.

All amps do not "sound great" just because they make speakers produce sound. I'd encourage the skeptics to check out the very, very few now doing Class D justice despite the message from the "all amps are great" crew.

I'm definitely a hearing is believing guy, so I'll away keep my ears open, and listen to all d-class amps I can get my hands on. I work on a lot of D class amps and so far it hasn't been much fun. Lots of new types of problems to solve or work around.

I wouldn't put much weight in my vote, its merely my opinion, and they are becoming mainstream, ready or not, anyway.
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post #176 of 210 Old 03-03-2016, 01:46 PM
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I'm definitely a hearing is believing guy, so I'll away keep my ears open, and listen to all d-class amps I can get my hands on.
Which ones have you heard?

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post #177 of 210 Old 03-03-2016, 03:09 PM
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I will say I sold an Parasound Halo A51 and switched to Crown amps (which are class D) and I just prefer the sound of class a/b amps and will be going back. Granted I didn't try the "high end" class D amps. I was going to order a Parasound Halo 31 for my L/C/R speakers but my dealer suggested the ATI Signature amps so that is what I ordered today. I am keeping all my Crown XLS 1502 amps to run my 4 surrrounds and 4 height speakers but for my L/C/R I think a quality a/b amp is my personal preference.
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post #178 of 210 Old 03-04-2016, 04:48 AM
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All switching based amplifiers currently have elevated noise floors, its just the current state in the evolution of this class of amplification.
Up to 135dB unweighted S/N ratio is called "elevated noise floor" in the current state of power amplifier evolution? Am I seriously behind of the current state?
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post #179 of 210 Old 03-05-2016, 05:39 AM
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Interesting what Anthem has to say about Class D:

http://www.anthemav.com/products-cur.../page=overview

Of course, they are trying to sell a product, and a very expensive one comparatively, but Anthem seems to believe in the superiority of Class D over A/B, at least in their own amp.

I suppose one could argue that'd they'd have to make such claims given the price as compared to their Class A/B designs. Where I would disagree with Anthem is that nobody else makes a good Class D amp (paraphrasing and my own interpretation of their words).
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post #180 of 210 Old 03-05-2016, 06:03 AM
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Interesting what Anthem has to say about Class D:

http://www.anthemav.com/products-cur.../page=overview

Of course, they are trying to sell a product, and a very expensive one comparatively, but Anthem seems to believe in the superiority of Class D over A/B, at least in their own amp.

I suppose one could argue that'd they'd have to make such claims given the price as compared to their Class A/B designs. Where I would disagree with Anthem is that nobody else makes a good Class D amp (paraphrasing and my own interpretation of their words).
I am an Anthem fan overall but I am not sure this class D offering is/was very well received as the reviews are not flattering:

http://www.soundandvision.com/conten...C9MUZkkiKKb.97
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